We interact with the physical world and influence events using the rules of causality. Most of us do this unconsciously, but there is advantage in understanding the process. This better enables us to verify our decisions.
Causality can be complex, with several causes combining to produce an effect. These causes can be of two types: necessary causes, in the absence of which the effect cannot occur; and sufficient causes, in the presence of which the effect must occur. The epidemiologist, Ken Rothman, explained that, for an effect to take place, it is often the case that several necessary causes must combine to create a sufficient cause. For example, the presence of gas, oxygen and a spark are each necessary and together sufficient to cause a gas explosion.
Causality also involves inhibitors, i.e., those things which always prevent an effect from taking place, even if sufficient cause is present. These inhibitors can also be of two types: sufficient inhibitors, in the presence of which the effect cannot occur; and necessary inhibitors, or those things required to prevent an effect. Again, a sufficient inhibitor may comprise one or more necessary inhibitors.
We can use this knowledge in our strategies to achieve a desired outcome. This is best demonstrated by a simple example. Suppose we know that an effect, e, occurs as a result of two necessary causes, a and b. Together, a and b are a sufficient cause. In the absence of a, b, or both, e cannot take place. So, if we wish to prevent e, then our strategy may be to prevent one of a or b, whichever is easiest. However, the effect can also be prevented by two sufficient inhibitors, c or d. In the presence of c, d or both, e cannot occur. Thus, an alternative strategy for preventing e, is to cause one of the inhibitors c or d, whichever is the easiest.
In this example, the presence of a and b and the absence of c and d result in e. If some but not all of these conditions exist, and e is undesirable, then this is a risk. However, if e is desirable, then it is an opportunity.
Our behaviour often steers events by increasing or decreasing their likelihood, rather than directly causing or preventing them. For example, we may lack the resources to directly cause an event, and may only have sufficient to enable it. To benefit from such behaviour, we must observe our environment, identify the opportunities and risks that it presents, and intervene to our advantage.
Typical strategies are as follows.
Enablement means acting to remove any existing inhibitors. Note that sufficient cause may not be present. So, the effect may not actually occur, but only become able to occur.
Facilitation means acting to introduce necessary causes where previously they were absent. Note that not all necessary causes may be present and not all inhibitors absent. So the effect may not actually occur, but merely become more likely.
Risk Reduction means acting to reduce the likelihood of an effect. It will not yet have occurred, either because an inhibitor is present, or because not all necessary causes are present. We can reduce the risk yet further by removing more necessary causes.
Prevention means acting to introduce an inhibitor where none is present. Note that the effect will not yet have occurred because not all necessary causes were present.